Luke Douglas - Please don't post in 7 month old solved topics or we might miss your post altogether. It's always better to create a new post of your own.
The small mobile range covers everything up to 30rem wide. Usually that is more that adequate as most mobiles are this wide. If you have some special requirements for specific devices then you can use your own media queries in custom CSS...
@media only all and (min-width: 0rem) and (max-width: 21rem) {
... your CSS goes here ...
}
Media queries work like this:
if the viewport size is xxxxx then
use this css
endif
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.